Meet Sunder, a New Way to Share Secrets

The moment a news organization is given access to highly sensitive materials—such as the Panama Papers, the NSA disclosures or the Drone Papers—the journalist and their source may be targeted by state and non-state actors, with the goal of preventing disclosures. How can whistleblowers and news organizations prepare for the worst?

The Freedom of the Press Foundation is requesting public comments and testing of a new open source tool that may help with this and similar use cases: Sunder, a desktop application for dividing access to secret information between multiple participants.

Sunder is not yet ready for high stakes use cases. It has not been audited and is alpha-quality software. We are looking for early community feedback, especially from media organizations, activists, and nonprofits.

While Sunder is a new tool that aims to make secret-sharing easy to use, the underlying cryptographic algorithm is far from novel: Shamir's Secret Sharing was developed in 1979 and has since found many applications in security tools. It divides a secret into parts, where some or all parts are needed to reconstruct the secret. This enables the conditional delegation of access to sensitive information. The secret could be social media account credentials, or the passphrase to an encrypted thumb drive, or the private key used to log into a server.

If you are interested in getting involved in development, we welcome your contributions! Please especially take a look at issues marked "easy" or "docs". Sunder is based on the open source RustySecrets library, which is also open to new contributors.

Sunder allows you to divide a secret into shares, a certain number of which are required to reconstruct it

How could Sunder be useful for journalists, activists and whistleblowers?

Until a quorum of participants agrees to combine their shares (the number is configurable, e.g., 5 out of 8), the individual parts are not sufficient to gain access, even by brute force methods. This property makes it possible to use Sunder in cases where you want to disclose a secret only if certain conditions are met.

The most frequently cited example is disclosure upon an adverse event. Let's say an activist's work is threatened by powerful interests. She provides access to an encrypted hard drive that contains her research to multiple news organizations. Each receives a share of the passphrase, under the condition that they only combine the shares upon her arrest or death, and that they take precautions to protect the shares until then.

Secret sharing can also used to protect the confidentiality of materials over a long running project. An example would be a documentary film project accumulating terabytes of footage that have to be stored safely. By "sundering" the key to an encrypted drive containing archival footage, the filmmaking team could reduce the risk of accidental or deliberate disclosure.

Disclaimer

As noted above, Sunder is still alpha quality software. It's very possible that this version has bugs and security issues, and we do not recommend it for high stakes use cases. Indeed, Sunder and the underlying library have not received a third party audit yet.

Furthermore, any secret sharing implementation is only as robust as the operational security around it. If you distribute or store shares in a manner that can be monitored by an adversary (e.g., online without the use of end-to-end encryption) this could compromise your security.

Inquiries

Credits

Sunder was primarily developed by Gabe Isman and Garrett Robinson. Conor Schaefer has acted as a maintainer and release manager; Lilia Kai recently also joined the project as a maintainer. RustySecrets was developed by the RustySecrets team. Conversations between Ed Snowden and Frederic Jacobs were the original impetus for the project.

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